Was US role in Afghanistan a failure or success? It depends, I would argue. If we are to go with the “Nation Building” doctrine that dominated US foreign policy two decades ago, then we can say the state of institutions in Afghanistan,after two decades of US direct intervention, is evidence of mission failure.
But if we view foreign policy as an extension of domestic policy priorities, then cant miss the fact that the US and the UK have long ago left the nation building approach.
I remember David Cameron jumping into the Obama wagon and publicly saying something along the line :” we are not in the nation building business “My point : you don’t expect US or UK to leave strong nation-state when they have clearly stated that they have changed course.
Nation building is expensive, and time consuming. US achieved its goal (serving its interest) and the Afghan lost.